The very high DC voltage based thumper method presently being used by most electrical power companies is unfortunately destructive to the original predicted life of any buried concentric ground type cable that it has been used on, as well as being potentially dangerous for people.
In my prior U.S. Pat. No. 5,428,295 issued June 1995 is disclosed a method of this general type but this has not achieved significant commercial success due to the problems principally with the dual opposing coil type receiver's antenna really operates not as well as what is discussed below.
Using the above method, whenever one tries to locate any High-Resistance Ground Faults within a buried concentric ground type cable using one of the current-crop of conventional Fault Locaters, one will almost always end up being defeated by that cable's excessively high capacitive reactive current. This is because at the tracing frequencies being used by most, if not all, of these current Fault-Locaters the concentric ground type cable's capacitive reactive current is always going to be totally overriding or masking the detection of almost every or any HRG Fault's resistive current. This in turn is because most, if not all, of those HRG Fault's resistive currents are almost always much smaller in scale than the reactive current being created by as little as a one foot of any buried concentric-ground type cable's capacity. Even when this is not the case, it is almost always going to be smaller than the reactive current being created by just a few feet of every concentric ground type cable's capacity.
Even when a 60 Hz 120 V rms is used as a trace-signal, only 34 feet of most buried concentric-ground type cables will create more reactive current than a single 1.0 Meg-ohm HRG Fault creates as its resistive current. Any of the usually used higher trace signal frequencies and any of the lower trace signal voltages that are usually used by most of today's Fault Locaters make them even worse off. By looking at the results that occur when using even a relatively low 510 Hz as the trace signal, (where it only requires less than 4.0 feet of most concentric ground type cables to duplicate in a reactive current the resistive current being created by a single 1.0 Meg-ohm HRG Fault), one can better understand the effects that most of the even higher more commonly used trace frequencies are going to cause.